There has heretofore been known an electronic musical instrument having means to produce a modulation effect. A complex modulation effect has been produced by means of a delay circuit, an example of such a device being shown in FIG. 1. In the device shown in FIG. 1, the musical tone signal input from the input terminal 1 is divided and supplied to two circuit systems D.sub.1 and D.sub.2. The component supplied to system D.sub.1 is amplified in an amplifier 4 and supplied to a speaker 6. The component supplied to system D.sub.2 is passed through a delay circuit 3, which is controlled by a modulator, amplified in an amplifier 5 and supplied to a speaker 7. The musical tone which is supplied the system D.sub.2, is, after having passed through the delay circuit 3, modulated by a delay time by means of the modulator 2, and is further influenced by the phase difference effect which may be produced between the musical tone signal which has been modulated in a complicated manner in the system D.sub.2 and the musical tone signal, which has passed straight through the system D.sub.1, so that there will be produced a rather complicated modulation effect by the above-described circuit. Thus, there has heretofore been attained a complicated modulation effect in a musical tone signal.